Project summary/abstract Reach-to-grasp and hand manipulation will be studied in tetraplegic humans with neural recordings from multielectrode arrays (MEAs) and intracortical microstimulation (ICMS) of somatosensory cortex. Recordings will be performed within the cortical grasp circuit with MEAs implanted in two grasp-related areas, the ventral premotor cortex (PMv) and the anterior intraparietal area (AIP) of the posterior parietal cortex (PPC). ICMS will be delivered to Brodmann's area 1 (BA1) of somatosensory cortex. Aim 1 will compare recordings from PMv and AIP to determine how grasping is processed by these two areas. We will test the hypothesis that AIP is more concerned with high-level goals and PMv more with motor trajectories. These results will be important for selecting areas for implantation for future neurosprosthetics development. Aim 2 will examine the tactile cues that can be provided by ICMS. We hypothesize that detection, discrimination, and location of stimuli will be perceived by varying parameters of frequency, amplitude and location of the ICMS. These findings will be used for providing stimulation induced tactile feedback for brain-machine interface (BMI) applications. In aim 3 we will use three tasks that combine decoding neural signals from AIP and PMv with ICMS for somesthetic feedback for a bidirectional BMI. The tasks will be used to test BMI performance (1) for frequency and amplitude discrimination of ICMS without visual feedback (?handbag task?), (2) for learning-based proprioception, and (3) a manipulandum task that implements force feedback for adjusting grasp. We hypothesize that the patients will successfully perform these tasks, indicating that bidirectional BMIs are feasible and can deliver tactile and proprioceptive information for grasp and hand manipulation. We have already developed artifact rejection techniques and demonstrated their application in a non-human primate (NHP) bidirectional BMI task. We also have all of the regulatory approvals for these studies and already have had success with BMI applications in tetraplegic patients using PPC recordings. Thus the outlook is good for successful completion of these aims within 3 years. The results of these aims will advance both the scientific understanding of grasp processing in human cortex and the development and implementation of bidirectional BMIs to assist patients with movement disorders.